Specific inhibition of one DNMT1-including complex influences tumor initiation and progression

Non-nucleoside inhibitors of DNMT1 and DNMT3 for targeted cancer therapy

DNA methylation can deactivate tumor suppressor genes thus causing cancers. Two DNA methylation inhibitors have been approved by the Food and Drug Administration (FDA) and have entered clinical use. However, these inhibitors are nucleoside analogues that can be incorporated into DNA or RNA and induce significant side effects. DNMT1 and DNMT3 are key enzymes involved in DNA methylation. In the acute myeloid leukemia model, a non-nucleoside DNMT1-specific inhibitor has shown lower toxicity and improved pharmacokinetics compared to traditional nucleoside drugs. DNMT3 is also implicated in certain specific cancers. Thus, developing non-nucleoside inhibitors for DNMT1 or DNMT3 can help in understanding their roles in carcinogenesis and provide targeted treatment options in certain cancers. Although no non-nucleoside inhibitors have yet entered clinical trials, in this review, we focus on DNMT1 or DNMT3 selective inhibitors. For DNMT1 selective inhibitors, we have compiled information on the repurposed drugs, derivative compounds and selective inhibitors identified through virtual screening. Additionally, we have outlined potential targets for DNMT1, including protein-protein complex, RNA mimics and aptamers. Compared to DNMT1, research on DNMT3-specific inhibitors has been less extensive. In this context, our exploration has identified a limited number of molecular inhibitors, and we have proposed specific long non-coding RNAs (lncRNAs) as potential contributors to the selective inhibition of DNMT3. This collective effort aims to offer valuable insights into the development of non-nucleoside inhibitors that selectively target DNMT1 or DNMT3.

Insights into DNMT1 and programmed cell death in diseases

DNMT1 (DNA methyltransferase 1) is the predominant member of the DNMT family and the most abundant DNMT in various cell types. It functions as a maintenance DNMT and is involved in various diseases, including cancer and nervous system diseases. Programmed cell death (PCD) is a fundamental mechanism that regulates cell proliferation and maintains the development and homeostasis of multicellular organisms. DNMT1 plays a regulatory role in various types of PCD, including apoptosis, autophagy, necroptosis, ferroptosis, and others. DNMT1 is closely associated with the development of various diseases by regulating key genes and pathways involved in PCD, including caspase 3/7 activities in apoptosis, Beclin 1, LC3, and some autophagy-related proteins in autophagy, glutathione peroxidase 4 (GPX4) and nuclear receptor coactivator 4 (NCOA4) in ferroptosis, and receptor-interacting protein kinase 1-receptor-interacting protein kinase 3-mixed lineage kinase domain-like protein (RIPK1-RIPK3-MLKL) in necroptosis. Our study summarizes the regulatory relationship between DNMT1 and different types of PCD in various diseases and discusses the potential of DNMT1 as a common regulatory hub in multiple types of PCD, offering a perspective for therapeutic approaches in disease.

Misregulation of the expression and activity of DNA methyltransferases in cancer

In mammals, DNA methyltransferases DNMT1 and DNMT3's (A, B and L) deposit and maintain DNA methylation in dividing and nondividing cells. Although these enzymes have an unremarkable DNA sequence specificity (CpG), their regional specificity is regulated by interactions with various protein factors, chromatin modifiers, and post-translational modifications of histones. Changes in the DNMT expression or interacting partners affect DNA methylation patterns. Consequently, the acquired gene expression may increase the proliferative potential of cells, often concomitant with loss of cell identity as found in cancer. Aberrant DNA methylation, including hypermethylation and hypomethylation at various genomic regions, therefore, is a hallmark of most cancers. Additionally, somatic mutations in DNMTs that affect catalytic activity were mapped in Acute Myeloid Leukemia cancer cells. Despite being very effective in some cancers, the clinically approved DNMT inhibitors lack specificity, which could result in a wide range of deleterious effects. Elucidating distinct molecular mechanisms of DNMTs will facilitate the discovery of alternative cancer therapeutic targets. This review is focused on: (i) the structure and characteristics of DNMTs, (ii) the prevalence of mutations and abnormal expression of DNMTs in cancer, (iii) factors that mediate their abnormal expression and (iv) the effect of anomalous DNMT-complexes in cancer.

Association of expression of epigenetic molecular factors with DNA methylation and sensitivity to chemotherapeutic agents in cancer cell lines

BACKGROUND

Altered DNA methylation patterns play important roles in cancer development and progression. We examined whether expression levels of genes directly or indirectly involved in DNA methylation and demethylation may be associated with response of cancer cell lines to chemotherapy treatment with a variety of antitumor agents.

RESULTS

We analyzed 72 genes encoding epigenetic factors directly or indirectly involved in DNA methylation and demethylation processes. We examined association of their pretreatment expression levels with methylation beta-values of individual DNA methylation probes, DNA methylation averaged within gene regions, and average epigenome-wide methylation levels. We analyzed data from 645 cancer cell lines and 23 cancer types from the Cancer Cell Line Encyclopedia and Genomics of Drug Sensitivity in Cancer datasets. We observed numerous correlations between expression of genes encoding epigenetic factors and response to chemotherapeutic agents. Expression of genes encoding a variety of epigenetic factors, including KDM2B, DNMT1, EHMT2, SETDB1, EZH2, APOBEC3G, and other genes, was correlated with response to multiple agents. DNA methylation of numerous target probes and gene regions was associated with expression of multiple genes encoding epigenetic factors, underscoring complex regulation of epigenome methylation by multiple intersecting molecular pathways. The genes whose expression was associated with methylation of multiple epigenome targets encode DNA methyltransferases, TET DNA methylcytosine dioxygenases, the methylated DNA-binding protein ZBTB38, KDM2B, SETDB1, and other molecular factors which are involved in diverse epigenetic processes affecting DNA methylation. While baseline DNA methylation of numerous epigenome targets was correlated with cell line response to antitumor agents, the complex relationships between the overlapping effects of each epigenetic factor on methylation of specific targets and the importance of such influences in tumor response to individual agents require further investigation.

CONCLUSIONS

Expression of multiple genes encoding epigenetic factors is associated with drug response and with DNA methylation of numerous epigenome targets that may affect response to therapeutic agents. Our findings suggest complex and interconnected pathways regulating DNA methylation in the epigenome, which may both directly and indirectly affect response to chemotherapy.

Effect of Epigenetic Drug Candidate Olsalazine on the Expression of CDH1 and uPA Genes in MCF-7 Breast Cancer Cell Line

Background: A main epigenetic change in cancer is DNA methylation, which leads to the inactivation of tumor suppressor genes. Due to its reversible nature, many studies have focused on how to correct epigenetic imbalances via inhibiting DNA methyltransferases (DNMTs). Recent studies have shown that olsalazine can be a potent candidate for DNMT inhibition. Objectives: The current study aimed to assess the cytotoxic effect of olsalazine on MCF-7 cells and the expression of CDH1 and uPA, as cancer-related genes, compared to decitabine. Methods: The cytotoxicity of olsalazine and decitabine on MCF-7 cells was assessed by MTT assay. To evaluate the effect of drugs on the expression of CDH1 and uPA genes, MCF-7 cells were treated with olsalazine and decitabine in concentrations below their IC50 values. After 24 h, RNA of treated cells was extracted and then subjected to a quantitative reverse transcription-polymerase chain reaction (Q-RT-PCR). Results: The MTT assay showed that olsalazine was more toxic (IC50 = 1.75 mM) in MCF-7 cells than decitabine (IC50 = 3mM). Q-RT-PCR analysis showed that olsalazine can significantly increase uPA expression along with a non-significant increase in CDH1 expression. Meanwhile, no significant change was found in gene expression after treatment with decitabine. Conclusions: This study demonstrated that olsalazine was more cytotoxic than decitabine on MCF-7 cells. Also, compared to decitabine, olsalazine could increase the expression of CDH1 and uPA genes. It suggests that olsalazine might be more potent than decitabine in inhibiting DNMTs, although further studies are needed.

De novo methyltransferases: Potential players in diseases and new directions for targeted therapy

Epigenetic modifications govern gene expression by guiding the human genome on 'what to express and what not to'. DNA methyltransferases (DNMTs) establish methylation patterns on DNA, particularly in CpG islands, and such patterns play a major role in gene silencing. DNMTs are a family of proteins/enzymes (DNMT1, 2, 3A, 3B, and 3L), among which, DNMT1 (maintenance methyltransferase) and DNMT3 (de novo methyltransferases) that direct mammalian development and genome imprinting are highly investigated. In recent decades, many studies revealed a strong association of DNA methylation patterns with gene expression in various clinical conditions. Differential expression of DNMT3 family proteins and their splice variants result in changes in methylation patterns and such alterations have been associated with the initiation and progression of various diseases, especially cancer. This review will discuss the aberrant modifications generated by DNMT3 proteins under various clinical conditions, suggesting a potential signature for de novo methyltransferases in targeted disease therapy. Further, this review discusses the possibility of using 'CpG island methylation signatures' as promising biomarkers and emphasizes 'targeted hypomethylation' by disrupting the interaction of specific DNMT-protein complexes as the future of cancer therapeutics.

Epigenetic protein complexes: the adequate candidates for the use of a new generation of epidrugs in personalized and precision medicine in cancer

Until recently, drug development in oncology was focused on treating most patients for a specific cancer type without taking in account the heterogeneity between these patients in term of response to treatment. Therefore, this type of broad treatment approach excludes the treatment of patient not responding to disease-specific common drugs. In this review, we focus on the different types of epigenetic drugs currently used as DNA methylation inhibitor agents and their limits in patient care due to their lack of specificity. We also highlight the emergence of a new type of epidrug with higher target specificity due to their original mechanism of action: the disruption of protein complexes involved in the epigenetic modifications.

Diuron exposure and Akt overexpression promote glioma formation through DNA hypomethylation

BACKGROUND

Diuron is an environmental component listed as a likely human carcinogen. Several other studies report that diuron can be oncogenic for bladder, urothelial, skin, and mammary cells. No study mentions the putative effect of diuron on the glioma occurrence.

OBJECTIVES

We here wanted to investigate the effects of diuron exposure on the glioma occurrence while wishing to incriminate a putative implication of DNA methylation modulation in this process.

METHODS

In in vivo model of glioma, diuron exposure was firstly compared or combined with oncogenic overexpressions already known to promote gliomagenesis. ELISA quantifying the 5-methylcytosine level on DNA was performed to examine the global DNA methylation level. Quantitative real-time polymerase chain reaction and proximity ligation in situ assay were performed to identify the molecular causes of the diuron-induced changes of DNA methylation. The signatures diuron-induced changes of DNA methylation were analyzed in a cohort of 23 GBM patients.

RESULTS

Diuron exposure is not sufficient to promote glioma, such as the oncogenic overexpression of Akt or Ras. However, the combination of diuron exposure and Akt overexpression promotes glioma. We observed that the diuron/Akt-induced glioma is characterized by three phenotypic signatures characterizing cancer cells: a global DNA hypomethylation, a loss of sensitivity to cell death induction, and a gain of signals of immune escape. Our data associated these phenotypes with three aberrant DNA methylation signatures: the LLT1, PD-L1, and Bcl-w hypomethylations. Strikingly, we observed that these three concomitant hypomethylations were only observed in GBM patients having a potential exposure to diuron via their professional activity.

CONCLUSIONS

As single player, diuron is not an oncogenic of glioma, but it can participate to the glioma formation in association with other events (also devoid of oncogenic property as single player) such as Akt overexpression.

Epigenetic Metalloenzymes

Epigenetics controls the expression of genes and is responsible for cellular phenotypes. The fundamental basis of these mechanisms involves in part the post-translational modifications (PTMs) of DNA and proteins, in particular, the nuclear histones. DNA can be methylated or demethylated on cytosine. Histones are marked by several modifications including acetylation and/or methylation, and of particular importance are the covalent modifications of lysine. There exists a balance between addition and removal of these PTMs, leading to three groups of enzymes involved in these processes: the writers adding marks, the erasers removing them, and the readers able to detect these marks and participating in the recruitment of transcription factors. The stimulation or the repression in the expression of genes is thus the result of a subtle equilibrium between all the possibilities coming from the combinations of these PTMs. Indeed, these mechanisms can be deregulated and then participate in the appearance, development and maintenance of various human diseases, including cancers, neurological and metabolic disorders. Some of the key players in epigenetics are metalloenzymes, belonging mostly to the group of erasers: the zinc-dependent histone deacetylases (HDACs), the iron-dependent lysine demethylases of the Jumonji family (JMJ or KDM) and for DNA the iron-dependent ten-eleven-translocation enzymes (TET) responsible for the oxidation of methylcytosine prior to the demethylation of DNA. This review presents these metalloenzymes, their importance in human disease and their inhibitors.

Amelioration of obsessive-compulsive disorder in three mouse models treated with one epigenetic drug: unraveling the underlying mechanism

Mental health disorders are manifested in families, yet cannot be fully explained by classical Mendelian genetics. Changes in gene expression via epigenetics present a plausible mechanism. Anxiety often leads to avoidant behaviors which upon repetition may become habitual, maladaptive and resistant to extinction as observed in obsessive compulsive disorders (OCD). Psychophysical models of OCD propose that anxiety (amygdala) and habits (dorsolateral striatum, DLS) may be causally linked. The amygdala activates spiny projection neurons in the DLS. Repetitive amygdala terminal stimulation in the DLS elicits long term OCD-like behavior in mice associated with circuitry changes and gene methylation-mediated decrease in the activity of protein phosphatase 1 (PP1). Treatment of OCD-like grooming behavior in Slitrk5, SAPAP3, and laser-stimulated mice with one dose of RG108 (DNA methyltransferase inhibitor), lead to marked symptom improvement lasting for at least one week as well as complete reversal of anomalous changes in circuitry and PP1 gene methylation.

miR-370-3p Is a Therapeutic Tool in Anti-glioblastoma Therapy but Is Not an Intratumoral or Cell-free Circulating Biomarker

In the last decade, microRNAs (miRs) have been described as biomarkers and therapeutic agents. Based on this finding, our aim here is to know if (1) miRNA-370-3p can be used as a biomarker associated with a favorable survival and if (2) miRNA-370-3p can be used as a therapeutic tool that increases the efficiency of standard anti-GBM treatment. A first approach using the data available on the “Prognostic miRNA Database” indicated that the expression level of miRNA-370-3p in GBM (T-miR-370-3p) is not associated with a prognosis value for survival. A second approach quantifying the expression level of cell-free circulating miRNA-370-3p (cfc-miR-370-3p) also indicated that cfc-miR-370-3p is not associated with a prognosis value for survival. To investigate whether miR-370-3p can be used in vivo to increase the anti-GBM effect of TMZ, we then used the model of LN18-induced GBMs in mice. Our data indicated that the miRNA-370-3p/TMZ treatment was two times more efficient than the TMZ treatment for decreasing the tumor volume. In addition, our study correlated the decrease of tumor volume induced by the miRNA-370-3p/TMZ treatment with the decrease in FOXM1 and MGMT (i.e., two targets of miR-370-3p).

Our data thus support the idea that miR-370-3p could be used as therapeutic tool for anti-glioblastoma therapy, but not as a biomarker.

The metabolism of 5-methylcytosine residues in DNA

The fundamental biochemical processes of 5-methylcytosine (5-mC) synthesis, maintenance, conversion and removal determine the time and spatial pattern of DNA methylation. This has a strong effect on a plethora of physiological aspects of cellular metabolism. While the presence of 5-mC within the promoter region can silence gene expression, its derivative - 5-hydroxymethylcytosine exerts an opposite effect. Dysregulations in the metabolism of 5-mC lead to an altered DNA methylation pattern which is linked with a disrupted epigenome, and are considered to play a significant part in the etiology of several human diseases. A summary of recent knowledge about the molecular processes participating in DNA methylation pattern shaping is provided here.

Under explored epigenetic modulators: role in glioma chemotherapy

Patients with somatic mutations of epigenetic regulators are characterized by aberrant chromatin modification patterns. Recent mechanistic studies pairing chemical tool compounds and deep-sequencing technology have greatly broadened our understanding of epigenetic regulation in glioma progression and underpinned alternative treatment of epigenetic inhibitors. However, the effect of most inhibitors is condition-dependent, and the overall results of clinical trials still have not been applied to patients. There is an intense need to develop more potent and specific compounds as well as identify the population who may achieve clinical benefits. Besides, combination therapy with conventional therapeutics is another alternative strategy. In this review, we summarize well-characterized chemical probes in glioma research and clinical translation. We also discuss the target population and combination of therapy regimens of various agents. In a holistic sense, we try to provide guidance for selecting targeted chemical probes and pave the way for personalized rational therapy.

Proteomic and Metabolomic Characterization of a Mammalian Cellular Transition from Quiescence to Proliferation

There exist similarities and differences in metabolism and physiology between normal proliferative cells and tumor cells. Once a cell enters the cell cycle, metabolic machinery is engaged to facilitate various processes. The kinetics and regulation of these metabolic changes have not been properly evaluated. To correlate the orchestration of these processes with the cell cycle, we analyzed the transition from quiescence to proliferation of a non-malignant murine pro-B lymphocyte cell line in response to IL-3. Using multiplex mass-spectrometry-based proteomics, we show that the transition to proliferation shares features generally attributed to cancer cells: upregulation of glycolysis, lipid metabolism, amino-acid synthesis, and nucleotide synthesis and downregulation of oxidative phosphorylation and the urea cycle. Furthermore, metabolomic profiling of this transition reveals similarities to cancer-related metabolic pathways. In particular, we find that methionine is consumed at a higher rate than that of other essential amino acids, with a potential link to maintenance of the epigenome.

Specific or not specific recruitment of DNMTs for DNA methylation, an epigenetic dilemma

Our current view of DNA methylation processes is strongly moving: First, even if it was generally admitted that DNMT3A and DNMT3B are associated with de novo methylation and DNMT1 is associated with inheritance DNA methylation, these distinctions are now not so clear. Secondly, since one decade, many partners of DNMTs have been involved in both the regulation of DNA methylation activity and DNMT recruitment on DNA. The high diversity of interactions and the combination of these interactions let us to subclass the different DNMT-including complexes. For example, the DNMT3L/DNMT3A complex is mainly related to de novo DNA methylation in embryonic states, whereas the DNMT1/PCNA/UHRF1 complex is required for maintaining global DNA methylation following DNA replication. On the opposite to these unspecific DNA methylation machineries (no preferential DNA sequence), some recently identified DNMT-including complexes are recruited on specific DNA sequences. The coexistence of both types of DNA methylation (un/specific) suggests a close cooperation and an orchestration between these systems to maintain genome and epigenome integrities. Deregulation of these systems can lead to pathologic disorders.

Silencing DNA methyltransferase 1 (DNMT1) inhibits proliferation, metastasis and invasion in ESCC by suppressing methylation of RASSF1A and DAPK

Our previous study showed DNMT1 is up-regulated in esophageal squamous cell carcinoma (ESCC), which is associated with methylation of tumor suppressors. In the current study, we investigate the role of DNMT1 in ESCC. We found silencing DNMT1 inhibited proliferation, metastasis and invasion of three different ESCC cells, K150, K410 and K450. We also found silencing DNMT1 induced G1 arrest and cell apoptosis in K150, K410 and K450 cells. In vivo study showed silencing DNMT1 suppressed tumor growth in nude mice. In addition, silencing DNMT1 increased expression of tumor suppressor genes, RASSF1A and DAPK, in ESCC cells and ESCC xenograft in nude mice. Moreover, silencing DNMT1 decreased methylation in promoter of RASSF1A and DAPK. In conclusion, our data demonstrated that silencing DNMT1 inhibits proliferation, metastasis and invasion in ESCC by suppressing methylation of RASSF1A and DAPK.

Specific Inhibition of DNMT3A/ISGF3γ Interaction Increases the Temozolomide Efficiency to Reduce Tumor Growth

DNA methylation is a fundamental feature of genomes and is a candidate for pharmacological manipulation that might have important therapeutic advantage. Thus, DNA methyltransferases (DNMTs) appear to be ideal targets for drug intervention.

By focusing on interactions existing between DNMT3A and DNMT3A-binding protein (D3A-BP), our work identifies the DNMT3A/ISGF3γ interaction such as a biomarker whose the presence level is associated with a poor survival prognosis and with a poor prognosis of response to the conventional chemotherapeutic treatment of glioblastoma multiforme (radiation plus temozolomide). Our data also demonstrates that the disruption of DNMT3A/ISGF3γ interactions increases the efficiency of chemotherapeutic treatment on established tumors in mice.

Thus, our data opens a promising and innovative alternative to the development of specific DNMT inhibitors.

Concerted changes in transcriptional regulation of genes involved in DNA methylation, demethylation, and folate-mediated one-carbon metabolism pathways in the NCI-60 cancer cell line panel in response to cancer drug treatment

BACKGROUND

Aberrant patterns of DNA methylation are abundant in cancer, and epigenetic pathways are increasingly being targeted in cancer drug treatment. Genetic components of the folate-mediated one-carbon metabolism pathway can affect DNA methylation and other vital cell functions, including DNA synthesis, amino acid biosynthesis, and cell growth.

RESULTS

We used a bioinformatics tool, the Transcriptional Pharmacology Workbench, to analyze temporal changes in gene expression among epigenetic regulators of DNA methylation and demethylation, and one-carbon metabolism genes in response to cancer drug treatment. We analyzed gene expression information from the NCI-60 cancer cell line panel after treatment with five antitumor agents, 5-azacytidine, doxorubicin, vorinostat, paclitaxel, and cisplatin. Each antitumor agent elicited concerted changes in gene expression of multiple pathway components across the cell lines. Expression changes of FOLR2, SMUG1, GART, GADD45A, MBD1, MTR, MTHFD1, and CTH were significantly correlated with chemosensitivity to some of the agents. Among many genes with concerted expression response to individual antitumor agents were genes encoding DNA methyltransferases DNMT1, DNMT3A, and DNMT3B, epigenetic and DNA repair factors MGMT, GADD45A, and MBD1, and one-carbon metabolism pathway members MTHFD1, TYMS, DHFR, MTR, MAT2A, SLC19A1, ATIC, and GART.

CONCLUSIONS

These transcriptional changes are likely to influence vital cellular functions of DNA methylation and demethylation, cellular growth, DNA biosynthesis, and DNA repair, and some of them may contribute to cytotoxic and apoptotic action of the drugs. This concerted molecular response was observed in a time-dependent manner, which may provide future guidelines for temporal selection of genetic drug targets for combination drug therapy treatment regimens.

The autophagy GABARAPL1 gene is epigenetically regulated in breast cancer models

Background

The GABARAP family members (GABARAP, GABARAPL1/GEC1 and GABARAPL2 /GATE-16) are involved in the intracellular transport of receptors and the autophagy pathway. We previously reported that GABARAPL1 expression was frequently downregulated in cancer cells while a high GABARAPL1 expression is a good prognosis marker for patients with lymph node-positive breast cancer.

Methods

In this study, we asked using qRT-PCR, western blotting and epigenetic quantification whether the expression of the GABARAP family was regulated in breast cancer by epigenetic modifications.

Results

Our data demonstrated that a specific decrease of GABARAPL1 expression in breast cancers was associated with both DNA methylation and histone deacetylation and that CREB-1 recruitment on GABARAPL1 promoter was required for GABARAPL1 expression.

Conclusions

Our work strongly suggests that epigenetic inhibitors and CREB-1 modulators may be used in the future to regulate autophagy in breast cancer cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1761-4) contains supplementary material, which is available to authorized users.

Activation of SAPK/JNK mediated the inhibition and reciprocal interaction of DNA methyltransferase 1 and EZH2 by ursolic acid in human lung cancer cells

BACKGROUND

Ursolic acid (UA), a pentacyclic triterpenoid, is known to have anti-tumor activity in various cancers including human non small cell lung cancer (NSCLC). However, the molecular mechanisms underlying the action of UA remain largely unknown.

METHODS

Cell viability was measured by MTT assays. Apoptosis was analyzed with Annexin V-FITC/PI Apoptosis Detection Kit by Flow cytometry. Western blot analysis was performed to measure the phosphorylation and protein expression of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), DNMT1 [DNA (cytosine-5)-methyltransferase 1], enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) and SP1. Exogenous expression of SP1 and DNMT1 was carried out by transient transfection assays.

RESULTS

We showed that UA inhibited the growth and induced apoptosis of NSCLC cells in the dose- and time-dependent fashion. Furthermore, we found that UA induced phosphorylation of SAPK/JNK and suppressed the protein expression of DNMT1 and EZH2. The inhibitor of SAPK/JNK (SP600125) blocked the UA-reduced expression of DNMT1 and EZH2. In addition, UA suppressed the expression of SP1 protein. Conversely, overexpression of SP1 reversed the effect of UA on DNMT1 and EZH2 expression, and feedback attenuated UA-induced phosphorylation of SAPK/JNK. Moreover, exogenous expression of DNMT1 antagonized the effect of UA on SAPK/JNK signaling, EZH2 protein expression, and NSCLC cell growth.

CONCLUSION

Our results show that UA inhibits growth of NSCLC cells through SAPK/JNK-mediated inhibition of SP1; this in turn results in inhibition the expression of DNMT1 and EZH2. Overexpression of DNMT1 diminishes UA-reduced EZH2 protein expression. The negative feedback regulation of SAPK/JNK signaling by SP1 and DNMT1, and the reciprocal interaction of EZH2 and DNMT1 contribute to the overall effects of UA. This study leads to important new insights into the mechanisms by which UA controls growth of NSCLC cells.

Berberine induces apoptosis in human multiple myeloma cell line U266 through hypomethylation of p53 promoter

Berberine has multiple pharmacological activities, such as anti-oxidative, anti-inflammation and anticancer activity. It reduces the proliferation and induces apoptosis in the multiple myeloma cell line, U266. Here we explored the detailed mechanism by analysing the gene expression profiles in U266 treated with or without berberine. DNMT1 andDNMT3B, encoding for a highly conserved member of the DNA methyltransferases, decreased significantly. By dissection of biochemical network database (BNDB) with Kyoto Encyclopaedia of Genes and Genomes (KEGG) annotation, the p53 signalling pathway related genes were altered. By using epigenetic chromatin modification enzymes PCR Array, gene expression microarray, RT-PCR and Bisulphite sequencing, the results show that berberine can repress the expression of DNMT1 and DNMT3B, which triggers hypomethylation of TP53 by changing the DNA methylation level and the alteration of p53 dependent signal pathway in human multiple melanoma cell U266.

Specific inhibition of DNMT1/CFP1 reduces cancer phenotypes and enhances chemotherapy effectiveness

AIM

DNA methylation is a fundamental biologic process of genomes and is a candidate for pharmacological manipulation that might have important therapeutic advantages. Thus, DNA methyltransferases (DNMTs) appear to be ideal targets for drug intervention.

MATERIALS & METHODS

To develop a new generation of DNMT inhibitor, we analyzed the ability of peptides to selectively inhibit certain DNMT1-incuding complexes.

RESULTS

Our study demonstrates that the disruption of DNMT1/CFP1-including complexes increases the efficiency of chemotherapeutic treatment on established tumors in mice.

CONCLUSION

Our data opens a promising and innovative alternative to the development of DNMT inhibitors.

DNA methyltransferase immunohistochemical expression in odontogenic tumours

BACKGROUND

Odontogenic tumours are a heterogeneous group of lesions formed from tissues that give rise to the tooth. DNA methylation, a covalent addition of a methyl group to the 5-carbon position of a cytosine nucleotide, is considered an important regulator of gene expression. The addition of the methyl radical is catalysed by DNA methyltransferases (DNMTs). Although some epigenetic studies have been conducted in odontogenic tumours, a study with the three types of DNMTs in several different members of this group is missing. This study analyses the expression of DNMTs in odontogenic tumours.

METHODS

Formalin-fixed and paraffin-embedded tissue samples of 20 ameloblastomas, 10 calcifying cystic odontogenic tumours, 10 calcifying epithelial tumours, 10 adenomatoid odontogenic tumours, 10 keratocystic odontogenic tumours, five ameloblastic fibromas, two ameloblastic fibro-odontomas, four central odontogenic fibromas, seven peripheral odontogenic fibromas and 10 odontogenic myxomas were included. Immunohistochemical expression of DNMT1, 3A and 3B was assessed using a semi-quantitative analysis, and also a correlation with p21, p27 and E-cadherin immunoexpression was made.

RESULTS

DNMT1, 3A and 3B were expressed in the nucleus and/or cytoplasm of all odontogenic tumours. DNMT1 expression was directly correlated with p27 expression in ameloblastomas.

CONCLUSION

The high expression of DNMTs in odontogenic tumour cells suggests methylation as an important mechanism for this group of tumours.

BET bromodomain inhibition suppresses transcriptional responses to cytokine-Jak-STAT signaling in a gene-specific manner in human monocytes

Disruption of the interaction of bromo and extraterminal (BET) proteins with acetylated histones using small molecule inhibitors suppresses Myc-driven cancers and TLR-induced inflammation in mouse models. The predominant mechanism of BET inhibitor action is to suppress BET-mediated recruitment of positive transcription elongation factor b and, thus, transcription elongation. We investigated the effects of BET inhibitor I-BET151 on transcriptional responses to TLR4 and TNF in primary human monocytes and also on responses to cytokines IFN-β, IFN-γ, IL-4, and IL-10, which activate the JAK-STAT signaling pathway and are important for monocyte polarization and inflammatory diseases. I-BET151 suppressed TLR4- and TNF-induced IFN responses by diminishing both autocrine IFN-β expression and transcriptional responses to IFN-β. I-BET151 inhibited cytokine-induced transcription of STAT targets in a gene-specific manner without affecting STAT activation or recruitment. This inhibition was independent of Myc or other upstream activators. IFN-stimulated gene transcription is regulated primarily at the level of transcription initiation. Accordingly, we found that I-BET151 suppressed the recruitment of transcriptional machinery to the CXCL10 promoter and an upstream enhancer. Our findings suggest that BET inhibition reduces inflammation partially through suppressing cytokine activity and expands the understanding of the inhibitory and potentially selective immunosuppressive effects of inhibiting BET proteins.

The DNMT1/PCNA/UHRF1 disruption induces tumorigenesis characterized by similar genetic and epigenetic signatures

Several genetic and epigenetic signatures characterize cancer cells. However, the relationships (causal or consequence link, existence due to a same origin) between these 2 types of signatures were not fully elucidated. In the present work, we reported that the disruption of the DNMT1/PCNA/UHRF1 complex acts as an oncogenic event of the tumor transformation of brain (astrocytes), breast, lung and mesothelial cells. We also show that these tumor transformation processes were associated with the acquisition of cancer hallmark and common genetic and epigenetic signatures. Thus, our data revealed that the global DNA hypomethylation induced by the DNMT1/PCNA/UHRF1 disruption is an oncogenic event of human tumorigenesis, an inducer of epigenetic and genetic signatures frequently observed in several human cancers, and is an initiator of oncogenic events.